Questions And Answers

We currently have an RTG tester and are using it to test table mats. Is there a site or a reference that can tell us the actual dissipative range of the table mat, so we can stay within ESD limits. -Mark, Fremont, CA

Answer

First, I assume that your RTG tester is a megohmeter; a meter that measures electrical resistance (surface) and resistivity (surface and volume) up to a Teraohm at 100 volts. For most ESD surface resistance measurements, the ANSI/ESD S4.1 had defined a megohmeter which used two 5 LB electrodes, settings of 10 or 100 volts between the electrodes, a measurement delay of about 10 seconds to minimize hysteresis and other non-linear measurements from various loaded materials such as carbon, among other constraints. The manufacturer of the ESD mat should be able to provide you with electrical specifications for that particular mat you are using and taking measurements on. In lieu of manufacturers specs, or in addition to them, you can refer to an ESD program Standard such as ANSI/ESD S20.20 which can be downloaded at: http://esda.org/pdf_files/s2020std.pdf